An LTE (Long Term Evolution) project evolves from 3G. The LTE project improves and enhances an over-the-air access technology of 3G, and improves performance of a cell-edge user. In an LTE system, reliability of information transmission is one of issues that an operator cares about, where reliable transmission of control information is a premise of normal communication.
In the prior art, a control information transmission method is provided, which is specifically: performing, in an LTE system, transmission of control information by using a PDCCH (physical downlink control channel). When a base station needs to send control information to UE, the base station first determines an aggregation level that is used for transmitting the control information, determines, from candidate PDCCHs included in search space corresponding to the aggregation level, a candidate PDCCH as a PDCCH carrying the control information, and sends the control information to the UE in a downlink subframe by using the PDCCH. The UE blindly detects, in the downlink subframe and in search space corresponding to each aggregation level, the PDCCH. When determining the PDCCH that the base station provides for the UE, the UE acquires the control information.
Since a base station can perform mapping and transmission of the control information in only one downlink subframe, reliability of control information transmission is relatively low.